1. Field of the Invention
The present invention relates in general to liquid crystal display devices and, in more particular, to a liquid crystal display device of the type which is called the xe2x80x9clateral electric fieldxe2x80x9d scheme.
2. Description of the Related Art
A liquid crystal display device of the type which is called the xe2x80x9clateral electric fieldxe2x80x9d scheme is arranged in a manner such that a pixel electrode and a counter electrode are formed on a surface on one transparent substrate side of respective transparent substrates which are disposed opposing each other with a liquid crystal being disposed between them, wherein the transmissivity of rays of light that transmit between these pixel electrode and counter electrode is controlled by twisting of molecules of the liquid crystal due to an electric field as created between the pixel electrode and counter electrode.
As apparent from this, the twisting of molecules of the liquid crystal is achieved by electric field components that are generated substantially in parallel with the transparent substrates. This is the main reason why the liquid crystal display device of this type is called the lateral electric field scheme.
Such a liquid crystal display device is capable of recognizing clear or xe2x80x9ccrispxe2x80x9d images even when observing them from a view point at an increased angle relative to the display plane thereof.
In order to increase and render uniform those components of the electric field generated within the liquid crystal which are in an almost parallel direction with the transparent substrates, it becomes important to establish a constant layer thickness of this liquid crystal in view of the fact that the liquid crystal thickness is also related thereto.
For this reason, a great number of bead-shaped distance pieces or spacer materials of the same diameter, for example, are disposed and scattered between the respective transparent substrates along with the liquid crystal, which substrates are disposed opposing each other.
These spacer beads are such that they are scattered on at least one substrate at a process step prior to assembly of two transparent substrates thereby allowing the spacer beads to reside between the transparent substrates.
However, it has been affirmed by vibration tests for device transportation that the liquid crystal display device with the above-mentioned configuration suffers from the risk of display irregularity which can occur due to movement of the spacer beads between the transparent substrates.
More specifically, this is because execution of vibration tests results in vibration of each of mutually opposing transparent substrates thereby causing the liquid crystal to flow and move, which in turn lets the spacers move accordingly whereby a change in orientation state thereof takes place at portions of an orientation film corresponding to such movement locus.
The present invention has been made by taking the technical background into consideration, and its object is to provide a liquid crystal display device capable of eliminating the display irregularity otherwise occurring due to movement of spacer materials.
A brief description of the summary of a representative one of the inventive principles as disclosed in the subject patent application is as follows.
In accordance with one aspect of the invention, a liquid crystal display device wherein a pixel electrode and a counter electrode are formed on a liquid crystal-side surface of one transparent substrate of respective transparent substrates which are so disposed as to oppose each other with a liquid crystal being laid therebetween, and wherein the transmissivity of light transmitting between these pixel electrode and counter electrode is controlled by twisting of molecules of the liquid crystal as caused by an electric field created between the pixel electrode and counter electrode, featured in that spacer materials are provided between respective ones of said transparent substrates, and that these spacer materials are fixed and disposed on an insulating layer underlying an orientation film which is in contact with said liquid crystal on the one transparent substrate side.
With the liquid crystal display device thus arranged, in view of the fact that the spacer materials placed between the transparent substrates are immovably mounted on the side of one transparent substrate, it becomes possible to eliminate movement of the spacer materials.
The spacer materials are arranged such that these are fixed to an insulating layer underlying an orientation film, and are also arranged so that they are covered and fixed by this orientation film.
This is in order that employment of the structure for causing the spacer materials to be also covered by the orientation film prevents an increase in a change of the state of orientation of liquid crystal around the spacer materials used.
Note also that in the case where the spacer materials are fixed to the orientation film, the arrangement is capable of avoiding the need for complicated works, such as ones which require addition of surface adhesion processing of the spacer materials.
In other words, this is because in the case the spacer materials are fixed to the insulating layer, it is possible to let the spacers tightly adhere to the insulating layer by forcing, for example, such spacers to scatter or distribute prior to hardening of the insulating layer and then effectuating appropriate heat application thereto in the hardening process.
In accordance with another aspect of the invention, the liquid crystal display device with the aforesaid configuration features in that said spacers are fixed to an insulating layer underlying an orientation film as contacted with said liquid crystal on the liquid crystal-side surface of the other transparent substrate of the respective transparent substrates.
The liquid crystal display device arranged as described above is configured in a manner such that the spacer materials are immovably attached to one specific transparent substrate of the pair of transparent substrates which is on the side with the pixel electrode and counter electrode not being formed thereon.
Due to formation of none of the respective electrodes, an insulating layer is typically formed underlying the orientation film which must be formed in contact with the liquid crystal; thus, it becomes possible to attain the intended arrangement capable of immovable attachment to this insulating layer without having to specially modify the configuration of any remaining portions.
By way of example, where an electrode (typically, formed beneath the orientation film) was formed on the transparent substrate on the side of adhesion of spacer materials, the electrode must be subject to design alteration or redesign, such as formation under the insulating layer, which would result in an electric field being created via the insulating layer between the electrode and another electrode associated therewith, thereby causing a problem that the electric field affecting the liquid crystal decreases in intensity.
It should be noted here that the term xe2x80x9cinsulating layerxe2x80x9d as used herein may principally refer to the other electrically insulative films, including a black matrix layer, color filter and any equivalents thereto.
In accordance with a further aspect of the invention, in the above-mentioned arrangement, said insulating layer is featured in that it is a flat, planarized film which covers a black matrix layer and a color filter.
The liquid crystal display device arranged as described above is configured so that a step-like difference, which may be formed due to layout of the black matrix layer and color filter with their portions overlapping each other, will no longer be observable on the surface thereof by the presence of the planarized film.
Accordingly, it is possible to make uniform the distribution layout of the spacer materials on the planarized film surface while simultaneously enabling adhesion on this planarized film to remain uniform.